FILAEIA GRACILIS. 91 



is an excellent example. "We may observe further, that Entozoa 

 are furnished with assimilative, excretory, and generative 

 organs ; that they are possessed of imperfectly developed nervous 

 and circulatory systems; and lastly, that peculiarities in the 

 form of individual members of the several groups, are sufficiently 

 striking to enable us in some cases, by the eye alone, and in 

 others by the aid of the microscope, to distinguish, not only 

 between species, but individuals of opposite sexes. 



We have ascertained then that the worms before us belong to 

 the l^ematoid or round worm order ; and we shall see presently 

 that they more particularly pertain to the genus Filaria, — they 

 are indeed fine specimens of the Filaria gracilis, a variety 

 discovered long ago by the celebrated helminthologist, 

 Eudolphi, whose work, written in the Latin tongue, is contained 

 in the library of the Microscopical Society in this Institution ; 

 and with the exception of the differences in the length of these 

 specimens and those described by him, together with two 

 tubercles, situated not upon the head, but near the extremity of 

 the tail, his description tallies with the result of my examination. 

 Owing to these differences, and never having seen on any 

 former occasion a worm of this species of the great length to 

 which these have attained, I forwarded one of them to Professor 

 Spencer Cobbold, of London, who kindly replied to the effect 

 that they were specimens of Filaria gracilis. The following 

 description will apply, except as to length, to all the specimens 

 freed from the peritoneum. 



Male worms. Length of the worm, minutely examined, 

 twenty-seven inches. It tapers from the middle to each 

 extremity, terminating abruptly at the head, which is conical, 

 depressed, and without tubercles, the tail being elongated, 

 pointed, and twisted several times upon itself; outer covering of 

 body exceedingly transparent, arranged distinctly in circles, 

 reflecting generally an emerald green light. General substance 

 of body semi-transparent, its caudal portion transparent through- 

 out its entire length. Layers of longitudinal muscular fibres can be 



